Self-Defence in Response to Attacks by Non-State Actors in the Light of Recent State Practice: A Step Forward?

Abstract

This article analyses the recent state practice in which the right of self-defence has been invoked in order to justify the use of force in response to attacks by non-state actors. The main purpose of this analysis is to determine whether the law of self-defence has evolved through this practice. It is submitted that the latter confirms the tendency, evidenced by the US operation 'Enduring Freedom' in Afghanistan in 2001, towards allowing states to respond in self-defence to private armed attacks, that is, attacks which are committed by non-state actors only. The article also aims to shed some light on other fundamental conditions of the law of self-defence which played a significant role in the legal assessment of the recent state practice. It is argued in this respect that this practice confirms that any armed attack must reach some level of gravity – which may be assessed by accumulating minor uses of force – in order to trigger the right of self-defence, and that proportionality of the action taken in self-defence may be assessed in quantitative terms, but only as a means of making a prima facie judgement about the necessity of this action.

Keywords: use of force, self-defence, non-state actors, Enduring Freedom, proportionality, private armed attack, Article 51, terrorism